OverviewThe Quanta 200 FEG Environmental Scanning Electron Microscope (ESEM) uses a field-emission gun (FEG) electron source in an exceptionally high chamber pressure environment. It combines two main advantages:
- Nanometer resolution and a high signal to noise ratio in both regular high vacuum and environmental (wet) modes.
- Real "wet" mode (100% humidity in the specimen chamber) and a possibility to examine specimens with a high vapor pressure in the chamber. It is provided by a differential pumping vacuum system and a series of pressure-limiting apertures in addition to a patented gaseous secondary electron detector.
Features and Specifications
Vacuum modesKey benefits of the Quanta 200 FEG Scanning Electron Micorscope are very short beam-gas path lengths for optimized beam brightness under gaseous conditions, and the high chamber pressures that can be achieved in the ESEM mode. The Quanta 200 FEG can be seamlessly switched between three vacuum modes enabling the investigation of conductive, non-conductive and high-vacuum incompatible materials. Available vacuum modes are listed below:
- High-vacuum (below 6 x 10-4 Pa) for imaging and microanalysis of conductive and/or conventionally prepared specimens
- Low-vacuum (10 to 200 Pa) for imaging and microanalysis of non-conductive specimens without preparation
- ESEM (10 to 2600 Pa) for high-vacuum incompatible specimens which are impossible to investigate with traditional EM methods
- Storage and recollection of sample position
- Double-click feature select function
- Multi-directional stage drive
- Compucentric rotation
- Stage navigation based on a pre-recorded image
Scanning systemThe Quanta 200 FEG provides a flexible scanning system controlled from the graphical user interface:
- Pixel density: 512 x 442, 1024 x 884, 2048 x 1768 or 4096 x 3536, selectable
- Dwell time: 50 ns/pixel (minimum) to 1 ms/pixel (maximum)
- Electronic scan rotation by 360 degrees
|High-vacuum mode:||conventional Everhart-Thornley detector with variable grid bias|
|Low-vacuum mode:||large-field, off-axis, gaseous secondary electron detector|
|High- and low-vacuum modes:||solid-state backscattered electron detector optimized for low-kV operation (down to 3 kV)|
|ESEM mode:||standard gaseous secondary electron detector, axially mounted|
|Source||Field emission gun assembly with Schottky emitter|
|Voltage||200 V to 30 kV|
|Beam Current||> 100 nA|
|Resolution||(measured as gold particle separation on a carbon substrate)|
– 1.2 nm at 30 kV (SE)
– 2.5 nm at 30 kV (BSE)
– 3.0 nm at 1 kV (SE)
– 1.5 nm at 30 kV (SE)
– 2.5 nm at 30 kV (BSE)
– 3.0 nm at 1 kV (SE)
|• Extended vacuum mode:|
|– 1.5 nm at 30 kV (SE)|
|Focus Range||2.5 – 99 mm|
|Field of View||Identical field of view in high- and low-vacuum modes (17 mm at the longest working distance), 500 µm with standard, axial, gaseous secondary electron (SE) detector|
When cooled between 0 and 10 °C, specimens of diverse nature can be imaged and analyzed at relative humidity conditions up to 100% (typical chamber pressures required are in the range 3-10 mbar). With the Peltier stage, humidity cycling experiments can be performed to characterize the sample's morphology and phase distribution at various relative humidity conditions. In-situ freeze-drying can be performed when the temperature range of the Peltier stage is set below 0 °C with a minimum of –20 °C. The temperature and the ramp-up profile are directly controlled through the Quanta user interface.
The 108 Auto is designed to operate in automatic or manual modes. Automatic operation gives a complete coating cycle using preset values for pressure, current and time. Manual operation is used for more difficult samples when a wider range of operating conditions is required.
The 108 Auto is fitted with separate argon gas circuits for (1) precision leaking and (2) flushing. This feature is important for the production of high quality stress-free coatings of Au/Pd, Pt/Pd, Au, Pd, and Pt. The system does not sputter Cr, Ni, Ag, Cu, Ir, or Ta.
The Cressington 108 Auto is designed as an integrated vacuum system with its desktop pumping system matched to the coating unit for optimum performance. The production of high quality coatings requires efficient gas handling in the range 0.05 mbar to 0.1 mbar.
In the past, sputter coaters for SEM have used the gas pressure control valve to adjust the sputtering current. The Cressington 108 Auto does not operate in this way: gas control and current control functions have been separated. This allows the user to independently adjust operating pressure (mbar) and sputter current (mA) to obtain the best sample conformity and minimum grain size. The rotary-planetary-tilting sample stage together with variable height sample chamber allows further optimization of the coating.
The Cressington 108 Auto can be factory fitted (or retro-fitted) with the optional MTM-20 thickness monitor system. For more information on the system and available accessories, please refer to Cressington and Ted Pella web sites.
Click on image to enlarge. The size of the slideshow can be adjusted with <Ctrl>+<+> and <Ctrl>+<-> keyboard shortcuts.
These are selected examples of images collected on Quanta 200 FEG by users of BM3 facility.
3D stereoscopic images
The red cyan(left and right eye respectively) 3D glasses are recommended to view these images correctly.